Wind erosion under cold climate: A Pleistocene periglacial mega-yardang system in Central Europe (Western Pannonian Basin, Hungary)

Mega-yardangs are known to form under extremely arid, warm or in some instances moderate climates. Here we report on the mega-yardang field of the Pannonian Basin (Hungary), which was uniquely formed under periglacial, probably semi-arid conditions, and discuss its implications on factors controlling yardang formation in general. The yardang field is composed of advanced, streamlined forms and of less aerodynamic ridges separated by well-developed corridors. The length of the largest features exceeds 60km, their height varies around 150m. Together with ventifacts, deflation hollows and wind-blown sand areas, the yardang field is part of an integrated eolian feature system driven by northerly to northwesterly winds. Dating of ventifact surfaces with in situ produced cosmogenic nuclides places the onset of significant wind erosion to the Early Pleistocene (1.5Ma). OSL-dated young loess, from which well-developed yardangs were sculpted, and wind-blown sands show that eolian action continued until the early Holocene. The long temporal range of wind erosion compared to average yardang formation rates and the rarity of advanced yardang forms indicate intermittent and relatively short, most probably millennial-scale deflation periods. Since the Early Holocene the system has been inactive, and demonstrates that yardangs can persist in a recognizable form for several millennia even under less arid conditions. The main control on yardang formation appears to be the existence of strong unidirectional winds, in the Pannonian Basin facilitated mainly by the channeling effect of topographic lows in the surrounding mountain chains. Yardangs can form even under semi-arid climates; however, the rarity of these occurrences suggests that this requires a special association of environmental conditions. Yardang formation is facilitated by homogeneous lithology, namely by widespread weakly consolidated, sandy sediments. The distribution of yardang fields is controlled by vertical neotectonic movements, which provided uplifted areas to be sculptured and topographic obstacles that sheltered downwind sediments. Faulting can be excluded as a controlling factor in mega-yardang formation, nor is the role of jointing supported.